1. Field of the Invention
The preset invention is directed to a vertical axis wind turbine having a plurality of blades arranged around a rotor shaft vertical to the ground. In particular, the present invention is directed to a vertical axis wind turbine incorporating a number of design improvements to provide a more effective and efficient wind turbine for generating electrical energy.
2. Prior Art
The use of wind turbines as a source of electrical energy has been utilized in various configurations in the past and is continued interest, given the increase in cost of fossil fuel as a source of power for electrical generators.
Two of the popular types of wind turbines are vertical axis wind turbines and horizontal axis wind turbines. The axis of the turbine is parallel to the ground and the rotor of a horizontal axis wind turbine generally faces into or away from the direction of the wind.
Various types of vertical axis wind turbines have also been proposed over the years. The Savonius wind turbine (such as seen in U.S. Pat. No. 1,697,574) including a pair of half cylinders mounted on a vertical shaft. The Savonius turbines are drag-type devices consisting of two or their half cylinders or scoops. Because of the curvature, the scoops experience less drag when moving against the wind than when moving with the wind.
Another type of vertical axis wind turbine is the Darrieus wind turbine (such as seen in U.S. Pat. No. 1,835,018) which consists of a number of airfoils mounted on a vertical rotating shaft or framework. The airfoils are arranged so that they are symmetrical and move forward through the air in a circular path. Relative to the blades, the oncoming airflow is added vertically to the wind, so a that the result in airflow creates a varying small positive angle of attack to the blade.
Other proposals for wind turbines include the following:
Kane (U.S. Pat. No. 7,040,859) discloses vanes 80 of a wind turbine 26 having a longitudinal axis 152 between 30° and 60° of the polar axis of the spheroid. The leading 100 and trailing 102 edges are elongated “S” curves. Each blade has a cross section of one half of an ellipse which is a poor airfoil. Each blade also has both leading and trailing edges rounded. Kane operates primarily as a drag or Savonius type device and its blade speed will be limited to the wind speed.
Obidniak (U.S. Pat. No. 4,915,580) discloses a wind turbine with blades comprising a body having a pair of opposed major planar surfaces and a cone or conoid shaped configured with a pair of opposed ends.
Robitaille (U.S. Pat. No. 6,448,668) discloses a turbine with curved blades which appear to be angled with respect to the axis.
Bartlett (U.S. Pat. No. 818,013) discloses a windmill with a plurality of longitudinally extending curved blades although each blade is parallel to the vertical axis.
Howard (U.S. Pat. No. 194,822) discloses a windmill with curved radial vanes B and B′, although each is parallel to the axis.
Ewers (U.S. Pat. No. 4,245,958) discloses a plurality of radially curved vanes.
Pfeifer (U.S. Pat. No. 1,764,052)discloses through shaped vanes 12 with upper and lower end closures.
Asperger (U.S. Pat. No. 4,031,405) discloses a windmill with radially extending curved vanes.
De Oviedo (U.S. Pat. No. 2,812,823) discloses a streamlined shape for vanes of a windmill.
Cymara (U.S. Pat. No. 4,260,325) disclosed a vertical axis windmill having vanes with U-shaped fins 32.
Benesh (U.S. Pat. No. 4,359,311) discloses blades 40, 41 and 42 having a curved portion 45 and an opposed inner edge 44.
Staley et al. (U.S. Pat. No. 5,391,926) discloses a vertical axis turbine with curved rotors extending from a shaft and double curved stators to direct wind to rotors.
Walters (U.S. Pat. No. 5,503,530 and 5,664,418) discloses a vertical axis turbine with impellers 4 having a triangular cross-section.
Becker (U.S. Patent Application Publication No. 2004/0061337) discloses a wind turbine with non-segmented smooth walled helically twisted inner turbine blades and a pair of opposed outer airfoil blades.
Nevertheless, there remains a need for an efficient wind turbine to be used to transform wind energy into electrical energy.